CN110011644B - Ring oscillator - Google Patents
Ring oscillator Download PDFInfo
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- CN110011644B CN110011644B CN201910311355.5A CN201910311355A CN110011644B CN 110011644 B CN110011644 B CN 110011644B CN 201910311355 A CN201910311355 A CN 201910311355A CN 110011644 B CN110011644 B CN 110011644B
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
- H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
- H03K3/027—Generators characterised by the type of circuit or by the means used for producing pulses by the use of logic circuits, with internal or external positive feedback
- H03K3/03—Astable circuits
- H03K3/0315—Ring oscillators
- H03K3/0322—Ring oscillators with differential cells
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Abstract
A ring oscillator comprises a bias current generating circuit, a PTAT voltage generating circuit, a frequency current converting circuit, a current comparison feedback circuit and a voltage-controlled ring oscillator; the bias current generating circuit is used for generating a positive temperature coefficient current and outputting the positive temperature coefficient current to the frequency current conversion circuit, and the PTAT voltage generating circuit is used for generating a positive temperature coefficient voltage and outputting the positive temperature coefficient voltage to the frequency current conversion circuit. By adopting the ring oscillator, the frequency drift caused by the change of the oscillation frequency along with the temperature can be obviously reduced, and the frequency drift does not change along with the change of the power supply voltage.
Description
Technical Field
The invention belongs to the field of electronic circuits, relates to an oscillator technology, and particularly relates to a ring oscillator.
Background
Oscillators are important components of electronic systems, providing accurate clock signals to the chip. The ring oscillator is a circuit which enables output signals to change according to a fixed period in a self-excitation mode, and has the characteristics of small occupied chip area and simple structure. The oscillation frequency of the existing ring oscillator is influenced by power supply voltage or ambient temperature, and large frequency change can be generated, so that the ring oscillator cannot meet the requirement of a high-precision system on clock frequency.
Disclosure of Invention
The invention provides a ring oscillator, which aims to solve the problem that the frequency variation range of the existing ring oscillator is large.
The ring oscillator comprises a bias current generating circuit, a PTAT voltage generating circuit, a frequency current converting circuit, a current comparison feedback circuit and a voltage-controlled ring oscillator;
the bias current generating circuit is used for generating a positive temperature coefficient current and outputting the positive temperature coefficient current to the frequency current conversion circuit, and the PTAT voltage generating circuit is used for generating a positive temperature coefficient voltage and outputting the positive temperature coefficient voltage to the frequency current conversion circuit;
the frequency current conversion circuit comprises an operational amplifier and an adjusting tube, the control end of the adjusting tube is connected with the output end of the operational amplifier, the input end and the output end of the adjusting tube are respectively connected with the bias current generating circuit and the inverting end of the operational amplifier, the output end of the PTAT voltage generating circuit is connected with the inverting end of the operational amplifier,
the frequency current conversion circuit also comprises a charging tube and a switch capacitor which are connected in series between the output end of the adjusting tube and the ground, the switch capacitor is connected with a discharge tube in parallel, a phase inverter is connected between the control ends of the charging tube and the discharge tube, and the input end of the phase inverter is connected with the output end of the voltage-controlled ring oscillator;
the current comparison feedback circuit is used for comparing the positive temperature coefficient current with the equivalent current on the switch capacitor and outputting a comparison voltage signal to the frequency control end of the voltage-controlled oscillator.
Specifically, the bias current generating circuit comprises a first NMOS tube and a drain-source short circuit which are connected in series between a power supply and the ground and are respectively connected in a diode mode.
Further, the current comparison feedback circuit comprises a second NMOS transistor and a first PMOS transistor which are connected between the power supply and the ground in series, and the grid electrode of the second NMOS transistor is connected with the grid electrode of the first NMOS transistor;
the current output tube is connected with the grid electrode of the first PMOS tube in a diode mode, and the output end of the current output tube is connected with the input end of the adjusting tube.
Further, the voltage-controlled oscillator has a frequency adjustment voltage input terminal, and the frequency adjustment voltage input terminal is connected to a common terminal of the second NMOS transistor and the first PMOS transistor.
Furthermore, a compensation capacitor is connected between the common end of the second NMOS tube and the first PMOS tube and a power supply.
Specifically, the voltage-controlled oscillator comprises a bias voltage circuit and N complementary MOS tube pairs which are connected in series; n is an odd number greater than 1;
the bias voltage circuit comprises a P bias tube and an N bias tube which are connected between a power supply and the ground in series, the N bias tube is connected in a diode mode, and a grid electrode of the P bias tube is used as a control voltage input end of the voltage-controlled oscillator;
each complementary MOS transistor pair comprises a plurality of devices connected in series between a power supply and the ground, a current adjusting PMOS transistor, a reverse NMOS transistor and a current adjusting NMOS transistor are sequentially arranged from the power supply to the ground, the grids of the reverse PMOS transistor and the reverse NMOS transistor are connected to serve as the input ends of the complementary MOS transistor pairs, the drains of the reverse PMOS transistor and the reverse NMOS transistor are connected to serve as the output ends of the complementary MOS transistor pairs, and the grids of the current adjusting PMOS transistor and the current adjusting NMOS transistor are respectively connected with the grids of the P bias transistor and the N bias transistor;
and the output end of the last stage of the complementary MOS transistor pair is connected with the input end of the first stage.
The ring oscillator can obviously reduce the frequency drift caused by the change of the oscillation frequency along with the temperature, and does not change along with the change of the power supply voltage.
Drawings
FIG. 1 is a schematic diagram of one embodiment of a ring oscillator according to the present invention;
fig. 2 is a schematic diagram of an embodiment of a voltage controlled oscillator according to the present invention;
the reference numbers in the figures refer to: c1-switch capacitor, C2-compensation capacitor, INV inverter, OP-operational amplifier, PTAT-PTAT voltage generating circuit, CLK-clock signal, D1-loss, N1-first NMOS transistor, N2-second NMOS transistor, N3-adjusting transistor, N4-charging transistor, N5-discharge transistor, N6-current adjusting NMOS transistor, N7-current adjusting NMOS transistor, N8-reverse NMOS transistor, P1-first PMOS transistor, P2-second PMOS transistor, P6-current adjusting PMOS transistor, P7-current adjusting PMOS transistor, P8-reverse PMOS transistor, vctrl-control voltage.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
The ring oscillator comprises a bias current generating circuit, a PTAT voltage generating circuit, a frequency current converting circuit and a voltage-controlled ring oscillator;
the bias current generating circuit is used for generating a positive temperature coefficient current and outputting the positive temperature coefficient current to the frequency current conversion circuit, and the PTAT voltage generating circuit is used for generating a positive temperature coefficient voltage and inputting the positive temperature coefficient voltage to the frequency current conversion circuit;
the frequency current conversion circuit comprises an operational amplifier and an adjusting tube, the control end of the adjusting tube is connected with the output end of the operational amplifier, the input end and the output end of the adjusting tube are respectively connected with the bias current generating circuit and the inverting end of the operational amplifier, the output end of the PTAT voltage generating circuit is connected with the inverting end of the operational amplifier,
the frequency current conversion circuit further comprises a charging tube and a switch capacitor which are connected in series between the output end of the adjusting tube and the ground, the switch capacitor is connected with a discharge tube in parallel, a phase inverter is connected between the control ends of the charging tube and the discharge tube, and the input end of the phase inverter is connected with the output end of the voltage-controlled ring oscillator.
The "positive temperature coefficient" refers to a current that increases with an increase in temperature, which is a positive temperature coefficient current, in the same trend as the temperature change, and as shown in fig. 1, one embodiment of the bias current generation circuit that generates a positive temperature coefficient current is given, and a depletion tube is used to generate a bias current with a positive temperature coefficient.
The bias current generating circuit comprises a first NMOS tube and a drain-source short circuit which are connected in series between a power supply and the ground and are respectively connected in a diode mode.
The current comparison feedback circuit comprises a second NMOS tube and a first PMOS tube which are connected between a power supply and the ground in series, and a current output tube, wherein the grid electrode of the second NMOS tube is connected with the grid electrode of the first NMOS tube;
the current output tube is connected with the grid electrode of the first PMOS tube in a diode mode, and the output end of the current output tube is connected with the input end of the adjusting tube
Although the drain electrode of the D1 is connected with the power supply, the grid electrode and the source electrode of the D1 are in short circuit and are connected with the grid electrode and the drain electrode of the N1, the source electrode of the N1 is connected with the ground, and the current generated by the circuit is the current flowing through the depletion tube D1, namely the current
Where u represents the carrier mobility, cox represents the gate oxide capacitance, W/L represents the width to length ratio of D1,
threshold voltage indicating D1And (6) pressing.
As can be seen from the embodiment shown in fig. 1, the current is input to the current comparison feedback circuit through the second NMOS transistor N2.
The current comparison feedback circuit comprises a second NMOS tube and a first PMOS tube which are connected in series between a power supply and the ground, and the grid electrode of the second NMOS tube is connected with the grid electrode of the first NMOS tube;
the current output tube is connected with the grid electrode of the first PMOS tube in a diode mode, and the output end of the current output tube is connected with the input end of the adjusting tube.
The current comparison feedback circuit inputs a positive temperature coefficient current through the second NMOS tube N2, inputs an equivalent current of a charging capacitor through the first PMOS tube P1, and takes a voltage reflected by a difference value obtained by comparing the positive temperature coefficient current and the equivalent current as a control voltage Vctrl of the voltage-controlled oscillator, so that the control voltage Vctrl of the oscillator obtains frequency feedback, frequency feedback is realized, and the frequency stability of the voltage-controlled oscillator is ensured.
The frequency current conversion circuit is used for converting the output clock frequency generated by the voltage-controlled ring oscillator into a corresponding current value;
the frequency-current conversion circuit is based on the equivalence of a switched capacitor C1 into a resistor and the application of a reference voltage on C1
The principle of conversion into current, thus realizing the conversion from frequency to current.
The method specifically comprises the following steps:
the positive temperature coefficient voltage Vptat generated by the PTAT voltage generating circuit is input to the positive phase end of the operational amplifier OP, the operational amplifier OP and the adjusting tube N3 are connected in series to form a feedback loop, so that a unit voltage gain buffer is formed, and the source voltage of the adjusting tube N3 is equal to the positive phase end voltage of the operational amplifier OP;
the output clock signal CLK of the voltage-controlled ring oscillator is connected to the grid of the discharge tube N5 and is connected to the grid of the charging tube N4 after being inverted by the inverter INV, so that the discharge tube N5 is turned on when the charging tube N4 is turned off, and the discharge tube N5 is turned off when the charging tube N4 is turned on, therefore, the switchThe voltage at the positive terminal of the capacitor C1 is repeatedly charged and discharged between the positive temperature coefficient voltage Vptat and the ground voltage to form a switched capacitor structure with a corresponding resistance value of
Wherein
Representing the frequency of the clock signal. Therefore, in the frequency-current conversion circuit, the equivalent current Ie is generated
The current and the positive temperature coefficient current generated by the bias current generating circuit are both 1: the copy ratio of 1 is equal at the time,
combining the vertical type 1 and the formula 2 to obtain
As can be seen from equation 3, the output clock frequency of the VCO
The power supply voltage is independent of the value of the power supply voltage, so that the power supply voltage is not influenced; in terms of temperature variation, the respective parameters in equation 4: u, cox W/L, C1 are all constant values, only
And Vptat varies with temperature, depleting the threshold voltage of the tube D1
Is a positive temperature coefficient value, so that it is only necessary to set the positive temperature coefficient reference voltage Vptat to be equal to
Have the same temperature coefficientValue of (2), clock frequency
The influence of the temperature is minimal.
The generation of the ptc voltage is a prior art in the art, for example, chinese patent CN106873704B discloses a ptc reference voltage source, and the details of the present invention are not repeated.
It should be noted that the above conclusion still applies even if the current mirror copy ratio is not 1.
A compensation capacitor C2 may be connected between the common terminal of the second NMOS transistor and the first PMOS transistor and the power supply, so as to filter high-frequency fluctuation on a control voltage Vctrl signal line of the voltage-controlled oscillator.
One embodiment of the voltage-controlled oscillator is shown in fig. 2, and the voltage-controlled oscillator includes a bias voltage circuit and N complementary MOS transistor pairs connected in series; n is an odd number greater than 1; n =3 in fig. 2.
The bias voltage circuit comprises a P bias tube and an N bias tube which are connected between a power supply and the ground in series, the N bias tube is connected in a diode mode, and a grid electrode of the P bias tube is used as a control voltage input end of the voltage-controlled oscillator;
each complementary MOS transistor pair comprises a plurality of devices connected in series between a power supply and the ground, a current adjusting PMOS transistor P7, a reverse PMOS transistor P8, a reverse NMOS transistor N8 and a current adjusting NMOS transistor N7 are sequentially arranged from the power supply to the ground, the grids of the reverse PMOS transistor and the reverse NMOS transistor are connected to serve as the input end of the complementary MOS transistor pair, the drains of the reverse PMOS transistor and the reverse NMOS transistor are connected to serve as the output end of the complementary MOS transistor pair, and the grids of the current adjusting PMOS transistor P6 and the current adjusting NMOS transistor N6 are respectively connected with the grids of the P bias transistor and the N bias transistor;
and the output end of the last stage of the complementary MOS transistor pair is connected with the input end of the first stage.
The voltage value of the control voltage Vctrl controls the clock frequency of the clock signal CLK output: when the control voltage Vctrl increases, the operating current of the inverter decreases and the clock frequency decreases
The size of the product is reduced; when the control voltage Vctrl decreases, the operating current of the inverter increases and the clock frequency increases
Then the size is increased; when the voltage of the control voltage Vctrl is stable, the working current of the inverter keeps a constant value, and the clock frequency
I.e. a stable value.
The foregoing are preferred embodiments of the present invention, and the preferred embodiments in the preferred embodiments may be combined in any overlapping manner if not obviously contradictory or prerequisite to a preferred embodiment, and the specific parameters in the embodiments and examples are only used for clearly illustrating the invention verification process of the inventor and are not used for limiting the patent protection scope of the present invention, which is still subject to the claims, and all equivalent structural changes made by using the contents of the specification and the drawings of the present invention shall be included in the protection scope of the present invention.
Claims (6)
1. A ring oscillator is characterized by comprising a bias current generating circuit, a PTAT voltage generating circuit, a frequency current converting circuit, a current comparison feedback circuit and a voltage-controlled ring oscillator;
the bias current generating circuit is used for generating a positive temperature coefficient current and outputting the positive temperature coefficient current to the frequency current conversion circuit, and the PTAT voltage generating circuit is used for generating a positive temperature coefficient voltage and outputting the positive temperature coefficient voltage to the frequency current conversion circuit;
the frequency current conversion circuit comprises an operational amplifier and an adjusting tube, the control end of the adjusting tube is connected with the output end of the operational amplifier, the input end and the output end of the adjusting tube are respectively connected with the bias current generating circuit and the inverting end of the operational amplifier, the output end of the PTAT voltage generating circuit is connected with the inverting end of the operational amplifier,
the frequency current conversion circuit also comprises a charging tube and a switch capacitor which are connected in series between the output end of the adjusting tube and the ground, the switch capacitor is connected with a discharge tube in parallel, an inverter is connected between the control ends of the charging tube and the discharge tube, and the input end of the inverter is connected with the output end of the voltage-controlled ring oscillator;
the current comparison feedback circuit is used for comparing the positive temperature coefficient current with the equivalent current on the switch capacitor and outputting a comparison voltage signal to a frequency control end of the voltage-controlled ring oscillator.
2. The ring oscillator of claim 1 wherein the bias current generation circuit includes a first NMOS transistor and a gate-source short connected in series between a power supply and ground and in diode form, respectively.
3. The ring oscillator of claim 2 wherein the current comparison feedback circuit comprises a second NMOS transistor and a first PMOS transistor connected in series between a power supply and ground, and a current output transistor, the gate of the second NMOS transistor being connected to the gate of the first NMOS transistor;
the current output tube is connected with the grid electrode of the first PMOS tube in a diode mode, and the output end of the current output tube is connected with the input end of the adjusting tube.
4. The ring oscillator of claim 3, wherein the voltage controlled ring oscillator has a frequency adjust voltage input connected at a common terminal of the second NMOS transistor and the first PMOS transistor.
5. The ring oscillator as set forth in claim 3, wherein a compensation capacitor is connected between a common terminal of the second NMOS transistor and the first PMOS transistor and a power supply.
6. The ring oscillator of claim 1, wherein the voltage controlled ring oscillator includes a bias voltage circuit and N complementary MOS transistor pairs connected in series; n is an odd number greater than 1;
the bias voltage circuit comprises a P bias tube and an N bias tube which are connected between a power supply and the ground in series, the N bias tube is connected in a diode mode, and a grid electrode of the P bias tube is used as a control voltage input end of the voltage-controlled ring oscillator;
each complementary MOS transistor pair comprises a plurality of devices connected in series between a power supply and the ground, a current adjusting PMOS transistor, a reverse NMOS transistor and a current adjusting NMOS transistor are sequentially arranged from the power supply to the ground, the grids of the reverse PMOS transistor and the reverse NMOS transistor are connected to serve as the input ends of the complementary MOS transistor pairs, the drains of the reverse PMOS transistor and the reverse NMOS transistor are connected to serve as the output ends of the complementary MOS transistor pairs, and the grids of the current adjusting PMOS transistor and the current adjusting NMOS transistor are respectively connected with the grids of the P bias transistor and the N bias transistor;
and the output end of the last stage of the complementary MOS transistor pair is connected with the input end of the first stage.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910311355.5A CN110011644B (en) | 2019-04-18 | 2019-04-18 | Ring oscillator |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910311355.5A CN110011644B (en) | 2019-04-18 | 2019-04-18 | Ring oscillator |
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| CN110011644A CN110011644A (en) | 2019-07-12 |
| CN110011644B true CN110011644B (en) | 2023-03-14 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111245432A (en) * | 2020-04-21 | 2020-06-05 | 成都启英泰伦科技有限公司 | Ring oscillator |
| CN113746455B (en) * | 2021-09-14 | 2024-03-12 | 北京欧铼德微电子技术有限公司 | Ring oscillator |
| CN115021726B (en) * | 2022-05-10 | 2023-02-17 | 上海韬润半导体有限公司 | Clock buffer circuit and analog-to-digital converter |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5180995A (en) * | 1991-09-13 | 1993-01-19 | Mitsubishi Denki Kabushiki Kaisha | Temperature-compensated ring oscillator circuit formed on a semiconductor substrate |
| CN1848667A (en) * | 2005-04-04 | 2006-10-18 | 凌阳科技股份有限公司 | Ring oscillator for compensating voltage source offset |
| CN103078635A (en) * | 2012-12-28 | 2013-05-01 | 杭州士兰微电子股份有限公司 | Embedded oscillation circuit |
| CN202998064U (en) * | 2012-12-28 | 2013-06-12 | 杭州士兰微电子股份有限公司 | An internally-disposed oscillation circuit |
| CN103312266A (en) * | 2013-05-06 | 2013-09-18 | 北京航空航天大学 | Design of circuit of annular oscillator insensitive to temperature |
| CN103618545A (en) * | 2013-11-26 | 2014-03-05 | 苏州贝克微电子有限公司 | High-frequency CMOS voltage-controlled oscillator |
| CN105099445A (en) * | 2014-05-12 | 2015-11-25 | 国家电网公司 | Frequency control method and circuit for ring oscillator |
-
2019
- 2019-04-18 CN CN201910311355.5A patent/CN110011644B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5180995A (en) * | 1991-09-13 | 1993-01-19 | Mitsubishi Denki Kabushiki Kaisha | Temperature-compensated ring oscillator circuit formed on a semiconductor substrate |
| CN1848667A (en) * | 2005-04-04 | 2006-10-18 | 凌阳科技股份有限公司 | Ring oscillator for compensating voltage source offset |
| CN103078635A (en) * | 2012-12-28 | 2013-05-01 | 杭州士兰微电子股份有限公司 | Embedded oscillation circuit |
| CN202998064U (en) * | 2012-12-28 | 2013-06-12 | 杭州士兰微电子股份有限公司 | An internally-disposed oscillation circuit |
| CN103312266A (en) * | 2013-05-06 | 2013-09-18 | 北京航空航天大学 | Design of circuit of annular oscillator insensitive to temperature |
| CN103618545A (en) * | 2013-11-26 | 2014-03-05 | 苏州贝克微电子有限公司 | High-frequency CMOS voltage-controlled oscillator |
| CN105099445A (en) * | 2014-05-12 | 2015-11-25 | 国家电网公司 | Frequency control method and circuit for ring oscillator |
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